[Bug math/13854] New: tan() is incorrect for large inputs on x86_64 and x86

["aj at suse dot de" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=13854

             Bug #: 13854
           Summary: tan() is incorrect for large inputs on x86_64 and x86
           Product: glibc
           Version: 2.13
            Status: NEW
          Keywords: glibc_2.15
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: unassigned@sourceware.org
        ReportedBy: aj@suse.de
                CC: aj@suse.de, bugdal@aerifal.cx,
                    carlos@systemhalted.org, ppluzhnikov@google.com,
                    vincent-srcware@vinc17.net
        Depends on: 13658
            Blocks: 13851, 13852
    Classification: Unclassified


+++ This bug was initially created as a clone of Bug #13658 +++

tan is inaccurate, see bug #13658 for a reference.

Test program:
#define _GNU_SOURCE
#include <stdio.h>
#include <math.h>


int main (void)
{
  volatile float xf = 1e22;
  float s1f, s2f;
  volatile double xd = 1e22;
  double s1d, s2d;
  volatile long double xl = 1e22;
  long double s1l, s2l;

  s1d = tan (xd);
  printf ("double: \n");
  printf ("x = %.17g\n", xd);
  printf ("s1 = %.17g\n", s1d);


  s1f = tanf (xf);
  printf ("\nfloat: \n");
  printf ("x = %.17g\n", xf);
  printf ("s1 = %.17g\n", s1f);

  s1l = tanl (xl);
  printf ("\nlong double: \n");
  printf ("x = %.17Lg\n", xl);
  printf ("s1 = %.17Lg\n", s1l);


  return 0;
}


On x86-64:
double: 
x = 1e+22
s1 = -1.6287782256068988

float: 
x = 9.9999997781963084e+21
s1 = -1.0810239315032959

long double: 
x = 1e+22
s1 = -0.52180662513577755

And on x86:
double: 
x = 1e+22
s1 = -0.52180662513577758

float: 
x = 9.9999997781963084e+21
s1 = -0.29305437207221985

long double: 
x = 1e+22
s1 = -0.52180662513577755

The correct result of tan (1e22) is:
s1 = -1.6287782256068988

-- 
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.